Theories and Observations
by Shivver
Summary: One cannot draw accurate conclusions when one does not have all the facts. (AU #2 for "The Actor", story #4)


**Author's Note** : This is the fourth story in AU #2 for my story _The Actor_. This is set after "A Scene from a Texas Diner", probably about month or so later. If it seems familiar, it's because it borrows concepts and scenes from "Discovery" (which I retconned from this AU).

These stories are being written out of order, so I apologize for any disconnect between them. Eventually, when they're all written, hopefully they'll feel cohesive and the character development is less jerky.

 **Spoiler Warning** : Requires _The Actor_ and _A Choice of a Lifetime_ ; won't make much sense without them.

* * *

Barely a day went by in David's life in which he didn't end up in a headlock before two hours had passed. He and Jenny started their daily skirmish on opposite ends of the gym, from which they warily danced closer to each other, waiting for the other to telegraph the wrong move or drop their guard for an instant. Taking advantage of either such opening, one fighter would move in to disable the other, usually in one fluid movement that immobilised their arms and caught their neck in the crook of an elbow. At least that's what David thought the experience might be like from Jenny's point of view; he certainly had no idea what it was like to win one of these contests. Jenny's superior training and fighting ability, brilliance at tactics, and grace and dexterity were more than a match for his greater strength and longer reach. He was learning, however, and only three days ago had managed to fight her off for three minutes. Today, however, he'd ended up in the stranglehold in less than twenty seconds; he hadn't done that badly in weeks. He'd been tripped and flipped over so fast that he had been stunned for a moment, and he coughed out a concession in Gallifreyan, pleased that the language was now so natural to him that it was the first to his lips when he wasn't thinking about it. Laughing, she released her hold on him and let him fall to his hands and knees.

"You weren't even trying that time, Big Brother. Your eyes gave it away, you know." She stepped back, wiping her hands with the satisfaction of a job well-done. "Distraction gives me any opening I want. What were you thinking about?"

"Sevratimonlan's _Temporal Mechanics, Grade 3_ ," he explained as he climbed back to his feet. "I've been trying to work through one of the examples in chapter five, and it's just not coming out. I've worked through it seven times, and I'm finding a variance of point five three at the very least, whereas he says it's point four eight. Tracing through his work, he assigns the dilation a factor of three point two and I don't see why. According to Ilitmilanderas, presence of gravitic bodies, however small, should contribute at least point six to it, and I'd argue for one point two due to the..." He trailed off as he looked up to see Jenny smirking at him in boredom. "What? I was hoping you'd tell me how you worked through it."

"Me?" She began stretching, even though they'd both limbered up before their battle. "I've not finished _Grade 1_ yet."

"Why not?"

"I just don't get temporal mechanics. It's hard to make it make sense." She shrugged. "And I don't speak Gallifreyan as well as you do. I'm spending too much time on looking up words and picking apart every sentence."

"I can understand that. The vocabulary and grammar for temporal phenomena is unusual at best."

"Obtuse." She jumped back to her feet. "Want to go again?"

He shook his head immediately, holding up his hands in a negation that he thought might look more like a surrender to her. "Not the sparring. You showed me that disarm technique yesterday. I'd like to practise that a bit."

"Okay!" She bounded over to the weapons cabinet and selected a practice knife to arm herself with. Turning around, she dropped into a ready stance. "Come at me!"

After about ten minutes of instruction and repeated attacks, David got to the point of being able to disarm Jenny three-quarters of the time. When he wasn't successful, he was rewarded with a stab in the stomach or a slice across an arm and Jenny's delighted laughter. However, he was confident enough with his technique that he began experimenting with variations of the move to catch her off-guard. When he executed a particularly smooth feint which ended with not only disarming the woman but also throwing her and pinning her to the mat, they grinned at each other, him with pride and her with a teacher's approval.

"You're really getting it, Big Brother!"

As she popped her chin up to peck him lightly on the nose, applause erupted from the doorway. "Excellent, David," the Doctor proclaimed, leaning against the jamb. "Perfect feint. You're getting better."

David let go of Jenny and as she rolled away and sprang to her feet, he sat back on his heels and studied the Doctor's expression to confirm the hint of condescension he'd detected in his tone. He sighed to himself; the man should know that he'd never had any martial training and couldn't be expected to excel at it this quickly. Determined not to rise to the Doctor's bait, he swallowed his irritation and replied with a flippant phrase. "I have to, or I spend the rest of the day bruised and sore."

The Doctor eyed Jenny, his pride in his daughter's excellence shining in his eyes. "Glad she's training you. It's always good to know how to defend yourself. You'll master it in no time, I'm sure."

Jenny retrieved the knife and jogged in place. "Want a go, Dad? Come get the dagger!"

The Doctor responded with an embarrassed smile. "Er, no. I prefer to keep my ego intact, thank you."

If he thought that might appease her, he was wrong. Jenny smiled with the gleam in her eye of a predator spotting easy prey. "Aw, come on! Just once." She dropped into a crouch and beckoned him with a hand.

Hopping up and stepping out of the way, David crossed his arms with a smirk. "Be careful what you ask for, Jenny. 'Dad' is not exactly untrained in martial arts, and he's seen a lot more combat than you have."

The Doctor pushed himself off the jamb. "And I didn't come here to wrestle. I've less physical instruction in mind."

"Oh, what's that?" Though it had been his own idea to get some combat training from Jenny, David was happy to cut the session short and save himself some pain. Jenny, however, looked disappointed. Whilst she did truly want to learn, book study was not her favourite part of the Doctor's curriculum.

"It occurred to me," the Doctor intoned as he strode into the gym, "that I've neglected an integral part of your education simply because it's a natural thing for Gallifreyan children, whether or not they become Time Lords, and they learn the basics almost before they can speak. I hadn't realised that it's not natural to either of you."

Both students were puzzled. "And that is?" asked Jenny, crossing her arms.

"Your psychic talents."

Whilst David nodded in understanding, Jenny continued to be confused. "What's that?"

"Well," the Doctor began, "even moderate psychic ability is extremely rare among humans and non-existent in the Hath, so the knowledge and training ingrained in you whilst you were in the progenation machine didn't include that subject. However, all Gallifreyans are psychic." That didn't help her understand what he was talking about, so he continued. "You've felt it, I know. Do you feel us, me and David, in your mind? Like you always know we're here, but not when we leave the TARDIS?"

"Yes, of course." Her eyes flicked between the two men. "That's because we're family, isn't it?"

"No, it's because you're psychic." The Doctor tapped his temple and flicked his finger toward hers. "You're able to reach out with your mind and touch other minds. If there were other Gallifreyans, you'd feel them, too."

"Oh." She frowned as she thought. "Humans don't feel this then?"

"Nope, they don't." The Doctor waggled his fingers at the side of his own head. "You can hear them a little, more like background noise than what you feel with us, but humans can't hear you or each other at all."

"Oh." Her face fell, sad like a child realising for the first time that others are less fortunate than herself. "They must be very lonely, then."

"No," David answered as the expert in this particular subject. "They're not. You can't miss what you've never had. It's not lonely if that's what you're used to. Humans bond through emotional and physical means, not mental ones."

"Like the way we talk and laugh together?"

"Right." David tapped the side of his head. "We just have that extra bit where we can sense each other, too."

Jenny chewed on the tip of her thumb as she thought. "I think I understand."

"Good!" The Doctor strode forward, rubbing his hands in anticipation. "Now, let's learn how to use this. Every Gallifreyan can sense each other, but there is more you can do, depending on your psychic strength and abilities. Most of us are strong enough to read others' minds and memories, and that's what we'll work on today. Some could move objects with their minds, and the strongest were able to hypnotise others, or even dominate them." Jenny looked horrified, so he hastened to reassure her. "Very good instinct, Jenny. Reading someone else's mind without their permission is already questionable, and forcing someone to do things against their will is far worse."

"Are you able to do that?" she asked, her eyes wide and apprehensive.

The Doctor nodded. "To some extent, yes. Took me a lot of practice. Some are far more talented, whilst others can't do it at all. But using it... Not something I do often, and only with very good reason." He eyed David, who was regarding him with a carefully neutral expression, then glanced away. "All right. Let's get started." He rubbed his hands together as he composed his words. "We do best when we're touching our subject. Some species work well without touch, but not us generally. Now, when I learned this, my tutor described a mind as divided into four layers. Don't think it's a good model to live by, because it's far too simple, but it serves its purpose, so I'm going to use it."

Using his hands to delineate layers, he marked out a flat level in front of himself. "Top layer. That's your existence. That's what you feel when you sense another. Every other layer is hidden behind our mental defenses. Deeper you go, the more you have to defeat the walls we put up." He made a punching motion directed at his flat other hand, to demonstrate breaking through layers. "Gallifreyans and other psychic races have good defenses, so they're difficult to break through. Non-psychic races have little defense, because they don't even comprehend what they're trying to keep out."

He then indicated levels beneath the one he had started with. "So, just below the top layer are the surface thoughts, what the person is thinking right now. Below that are the memories, and below that, at the very core of the person, is the person himself, his personality, his moral construction, his wants and needs." He demonstrated the last concept with his balled fist below all of the other layers. "Get there, and bam! You control the person."

The Doctor glanced at each of his students to make sure they understood so far and they nodded, Jenny more tentatively than David. "To read a person's surface thoughts, you aren't going too deep, but to see their memories takes more strength and skill. Then, to manipulate who they are and what they do takes more than most of us have." He grinned. "Which I suppose is a good thing. Anyway, there are two ways to do that. One is to subtly convince them to do it, and that's hypnosis, and it's a bit easier, if not reliable. The other is to force them, and that's domination. The second is far harder, because the person will be fighting you all the way, whether or not they know that they're fighting. Only the most powerful psychics can completely dominate another person, and even then, it's not easy.

"Today, we'll work on getting to that second layer, the surface thoughts. Best to start slow and easy. Jenny, you'll go first." She bounced with excitement. "Come stand in front of me." Taking her by the shoulders, he positioned her squarely in front of himself. "Now, you need to touch me, skin to skin. Anywhere is fine, but closer to the brain helps. Go ahead and do that." He closed his eyes.

Jenny reached up with both hands and placed them on the Doctor's cheeks, her fingers slightly spread. "You're too tall. Like this?"

"A good start. You'll decide for yourself if you like that placement. Now." He opened his eyes and gazed down at her. "You should feel a bit of a stronger connection with me." He waited for her to nod. "Follow that connection and push into my mind. I'm not going to let my guard down, so you'll feel resistance and you'll need to push through, and find the concept that I'm thinking of. Ready?"

She closed her eyes. "Yes."

"Go." He closed his eyes again.

After a few seconds of silence, Jenny grimaced, concentrating hard. The Doctor nodded, though not enough to interrupt Jenny's touch. "Push harder. Don't worry. It doesn't hurt."

"There's a... there's a... a line, like a trail. A trail of thought."

"Yes, that's it," the Doctor replied with gentle encouragement. "Follow it in, and forge ahead when you feel you're being blocked off."

She grunted. "I can't. It's too hard to push through."

"You can do it. Try harder. Don't be afraid that you're going to hurt me."

"Okay..." Another few seconds later, Jenny's eyes popped open. "Hot fudge sundae?"

The Doctor shrugged. "Well, I thought we might go out for sundaes after. There's this fantastic ice cream parlour in Chicago, in 1960..." Catching himself from going on his tangent, he grinned at her. "A brilliant first try!"

Her smile bright and proud, she shifted her hands into a hug. "Thanks, Dad!"

"We'll practise more, but first, let's let David have a go." With a sudden frown, he glanced at David. "If you want."

David had been quietly standing off to the side, apprehensive about trying this new thing. Though he'd abandoned identifying himself as human for over half a year now and he'd been studying Gallifreyan language and Time Lord technologies, this was the first innately alien thing he was going to attempt to do, and the mere thought of it made him a bit nauseous. It didn't help that he realised, whilst the Doctor was talking, that he'd known that the Doctor had used his power of hypnotism and suggestion on occasion but had not made the connection that he might be able to do the same thing. And finally, it sickened him to think that he was about to learn to do what that Polthite, Ana, had done to him, that had left him helpless and violated. He knew the Doctor's methods were far gentler and kinder, but they still felt like the same outcome.

He peered back at the Doctor, one eyebrow cocked, trying to decipher the man's cryptic expression. Was the Doctor somehow aware of David's apprehensions? Or did he suspect that David might not be able to do this at all? After all, he was part human and humans weren't psychic; that might just be enough to weaken his mind, limiting his abilities. Or perhaps the Doctor's hesitation was indicative of what David had guessed all along, that he didn't truly want David here at all and was training him out of some sense of obligation to the creature he'd created, and that this was just another onerous task he had to undertake. However, there was no way to tell, and David knew that he needed to learn how to utilise his now-natural abilities.

"Yeah. We need to. All right. Let's do this," he heard himself say with more enthusiasm than he felt.

"Quite." The Doctor set his jaw with determination. "I think you know what to do." David nodded.

As Jenny stepped to the sidelines, David positioned himself in front of the Doctor. Being a clone of the man came in handy: they were the same height and he didn't need to reach high like Jenny had. As the Doctor closed his eyes, David placed his fingers carefully on his temples, the same way he had done it when he'd played a similar scene out with Sophia Myles' Reinette.

Immediately, he felt a tighter connection with the Doctor, and he sensed, in addition to the mental barrier in front of him, some amount of reluctance, maybe even a fear of mental contact. This further evidence of the Doctor's indifference to himself grieved David, but he pushed that thought out of his mind; from the episode with Reinette, he was well aware that though he'd be the one searching the Doctor's mind, the Doctor would be perfectly capable of viewing his as well, and he didn't need his host and teacher knowing that he was aware he wasn't wanted here. From a distance, he heard the Doctor say, "I doubt I need to give you any instruction. Push firmly and tell me what concept I'm thinking of." David took a deep breath, focused his mind through the link between himself and the Doctor, and pushed.

The sensation of forcing his way into another mind for the first time ever almost made David recoil. He'd always assumed that mind-reading was like bursting through a door and walking into a room, that once there, he see the person's thoughts on the walls, or hear them as voices, but it was nothing like that. Instead of a direct insertion, a lance of thought punching a hole through the Doctor's defenses, it felt more like... he supposed it must be like what water would feel like being forced through a fine sponge: his mind was pushing into and blending with the Doctor's, and he had to concentrate to focus, to fight a sensation of his self dispersing, dissolving into that of the man in front of him. Once he felt he was back in control, he allowed himself a moment to get his bearings. Though, with his eyes open, he could see his own fingers splayed on the Doctor's temples, he could also feel his own fingertips on his face - the Doctor's, not his own - disorientating him. He concentrated, and yes, he could distinguish between the Doctor's sensory input and his own. He suspected he'd need to practise to do that naturally.

 _Oh, right, what's he thinking?_ A maelstrom of stray thoughts - both his and the Doctor's - whirled through his mind, but one shone brighter than the rest. "Tenor saxophone?" he asked as he frowned at the Doctor in disbelief.

One eye creaked open. "There were too many things you'd just be able to guess. Had to choose something you weren't expecting." The Doctor stepped back, out of David's grasp. The younger Time Lord shook his head, trying to dispel the the lingering sensation of being in the Doctor's head. "Are you all right, David?" Concerned, the Doctor stepped forward again, one hand stretched toward his student, though with a glance at David's face, he snatched it back behind his back. "You look a bit disconcerted."

"I'm fine." With one hand, David rubbed at the side of his head. "It's not at all what I expected. I -" He had been about to comment that the Polthite's telepathy had felt completely different but stopped himself. The Doctor, who had turned to look over at Jenny, wouldn't be interested in hearing about his experience.

"I suspect not. It's not quite like anything else, is it? You're feeling okay?" The second question was directed at Jenny.

"Just fine, Dad," she responded with a cheery smile.

"Good." Jamming his hands in his pockets, the Doctor turned back toward David. "Excellent work. I don't know if you're stronger than Jenny, but you're certainly much more confident, and that helps quite a bit." Spinning on his heel, he called, "Come on!" as he strode toward the door.

"We're not going to practise more?" Jenny frowned her disappointment.

The Doctor spun back in the doorway. "Not now. You've homework to do. You should both think about what it felt like and what you'd do differently, before we try again. And think about how you'd sort through all those extra thoughts and emotions to get what you're looking for, because it's not easy. And besides," he grinned, "there's ice cream to be had."

Jenny's wide, excited smile matched his and she bounded forward to take her place by her father. Turning back, she called, "Come on, Big Brother!"

"Nah. You go on." David forced an affectionate smile at them; he knew how to pretend to appear sincerely happy. "I've things I want to do, and I'm really not hungry." He saw the Doctor's eyebrow shoot up as a hint of suspicion flitted across his face. "Enjoy yourselves."

"You sure?" she coaxed once more as she slipped her hand into the Doctor's.

"Yeah. Enjoy, you two." He felt a bit foolish standing alone in the center of the empty practice room.

"Come on." The Doctor tugged at Jenny's hand. "Don't work too hard, David," he advised as they strolled out.

"Yeah," David murmured to himself as he swung his arms around. He waited a moment before heading out himself.

. _ . _ . _ . _ .

With his study tablet and his leather-bound copy of Sevratimonlan's _Temporal Mechanics, Grade 3_ clutched to his chest, David strode down the corridor toward the library. He smiled as he eyed the coppery walls illuminated by a soft, warm light; the TARDIS interior he had seen on the telly had always felt a bit stark, bright white and impersonal, but this was much more inviting and comfortable. He was confident that his interpretation of the atmosphere was not coloured by his ability to feel the capsule's ambient breath.

The difficulties he was having with his studies had been preoccupying him all day, through the sparring and the telepathy lesson, and though he might have been doing other things, one of the problems in the chapter churned through his mind over and over again. Up until this topic, he'd had no problems with temporal mechanics and had been rather enjoying his studies, feeling for the first time that his not-quite-Time-Lord brain was keeping up with the curriculum. In fact, he had enjoyed the subject so much that he'd gone beyond the Doctor's recommendation, which had been mastering Sevratimonlan's texts for grades one through five, and searched the library for supplemental material that he could understand at his novice level. Then, in the last few chapters, it had stopped making sense. As he wrestled with the theory, data, and calculations, he became more and more frustrated: no matter what he did, he couldn't reconcile the three and produce the answers that the author expected, and the problem currently looping through his mind was only one of the many examples he couldn't work through. _Just what am I doing wrong?_ he berated himself.

He'd spent twenty hours - _well, nineteen hours, forty-three minutes to be exact…_ \- working through this one problem over and over again to no avail, and it was time to seek help. Of course, the smart thing to do would be to ask the Doctor, but David was not quite ready to swallow his pride. He didn't need to demonstrate yet again how much less of a Time Lord he was than either the Doctor or Jenny, how much his humanity limited what he could achieve, and he certainly didn't want to make the Doctor regret even more that he'd agreed to train him. Besides, it was always good to do your own research and exhaust all of the available resources before begging for help. Perhaps he wasn't clever enough, but at least he was hard-working and self-reliant.

He prided himself that those attributes came from his human side, from the personality of the man he used to be. He'd always pursued his interests - _Doctor Who_ , acting, music, to name a few - with zeal bordering on obsession, and this had translated through his transformation into a Time Lord. He did wonder, though, if this trait of his hadn't been magnified in the process. Spending twenty hours on a single homework problem might be a bit excessive - and he was about to spend more - and even the Doctor complained that he never raised his nose out of his books except to eat and sleep, and those not often. David clenched his fists around his study materials as he walked. The problem was time, something that, ironically, he didn't have. Training at the Academy on Gallifrey spanned a hundred years; how much time did he have to learn all of that? The Doctor never mentioned a schedule, but David doubted it would be long: a couple of years, maybe. He clapped a hand to his chest to calm the panicked fluttering of his hearts whenever he consciously thought about it. He, a strange Time Lord/human hybrid, had to learn fifty times faster than a real Time Lord, and this was assuming the Doctor didn't suddenly decide that he'd fulfilled the letter of his promise to train him and dump him on a curb in Aberdeen. Every moment he spent studying just never felt like it would be enough.

Shouldering the thick mahogany door open, David stepped into the TARDIS library. He'd spent enough time in here - first as a human devouring every new play he could find and then as a Time Lord supplementing his education - that even though its appearance and layout changed every few sleep cycles, it felt more like home than his own bedroom and he never got lost in it, even though it was larger than he'd had a chance to explore and was sure to have secrets hidden away. Today it appeared like it had the last time he'd been here, with rows and rows of walnut shelves with alcoves of cushy chairs and coffee tables tucked away here and there. Selecting a study area, David dropped his things on a table and set off for the science and engineering section.

Over three hours later, David flopped back in his chair, ready to fling his books out of the TARDIS doors into deep space. He'd found two tomes that dealt with the subject matter in chapter five and after working through them, he was now even more confused: applying the concepts in these books made the calculations produce even worse results than he'd gotten before. It didn't help that the new material seemed so easy, so intuitive. Nothing fit. Growling under his breath, he shook his fists impotently at the papers in front of him. There had to be something he was missing, something he hadn't learnt yet that would settle everything into place.

Jumping up, he stomped off among the shelves, looking for that fabled text that would solve all of his problems, but he'd been through all of this before and had combed through the catalogue, and there just weren't other applicable books he hadn't seen yet. There were a few advanced texts that he'd glanced through, but the topic he was working on, spatio-temporal variances from grade three of a thirty-four-year curriculum, was so basic, they made no mention of the theory behind a subject in which a reader would be expected to be an expert. He began wandering other sections of the library, hoping that the right book would be hidden among the travel guides, historical romances, cookbooks, and other miscellany from all over the known galaxies. He soon discovered rooms that opened off the main library, housing special collections, such as an array of originals of works by human authors starting from Murasaki Shikibu; he could tell from the way his senses hitched and buzzed as he entered the room that it was held in temporal stasis when unused, to preserve the works from aging. There were many such rooms, but he found nothing in them that could help him with his studies.

As he prowled the shelves, another door caught his eye and he went to investigate. The chamber behind the door was like nothing he'd seen before in the library. Instead of the leather-bound books and tightly-wound scrolls stuffed on the shelves like in all of the other rooms, he found thousands of translucent cubes, a bit less than a centimetre on a side, packed together on racks that stretched from floor to ceiling, mounted on sliders, so that he could page between them easily. There were no labels or instructions, nothing else except a single cube sitting in a ceramic bowl on a table near the door. He stepped up to one of the shelves and peered closely at its contents, but could discern no difference between one cube and its identical neighbour; they seemed perfectly formed and meticulously aligned with each other.

David was loathe to leave his fingerprints on the shiny, dustless cubes, but he wanted a closer look, so he reached out to pick one up and almost tumbled backwards off his feet as the meta information about it coalesced in his mind. _A psychic library!_ Designed by touch-telepathic Time Lords, each cube seemed to contain one book. Closing his eyes, David concentrated to explore the book, a treatise on Matrix manipulation, and was pleased to find that though the subject matter was far beyond his comprehension, it was intuitive to search through and read its contents.

Placing the cube back on the shelf, he returned to the door and touched the cube in the bowl. It was exactly what he suspected: a catalogue of the contents of the room. His mind filled with an expanding cloud of titles, topics, and synopses through which he flew with ease, identifying individual motes with the information he was searching for. Selecting six promising tomes, he fixed their locations in his mind, then strode to the shelves to pick out the crystal books. It was a little disorientating to have the meta information from the cubes in his hand floating around in his head and he practised shutting away the psychic impressions as he returned to the centre of the room and sat down on the floor.

Arranging the cubes in a row in front of himself, David laid a fingertip on the first book and focused his attention on it. Riffling through the information contained within, he recognised it as being within his comprehension level and nodded with satisfaction. The second book he touched was obviously far too advanced for him: not only were the concepts beyond anything he'd seen before, but many of the Gallifreyan words were unfamiliar. He flicked that book out of the row with a finger.

The third book was much more in line with what he was looking for. A particularly interesting chapter caught his attention, and he was soon engrossed in it. He found that studying in this manner was far easier than with a physical book or a tablet: data retrieval was instantaneous and he could rearrange the subject manner in any way he needed to help himself learn. It was simply natural to connect different parts of the book together in any way he saw fit.

One particular concept piqued his interest and, remembering that it had been mentioned in the first crystal book he'd looked at, without thinking, he reached out with his other hand to touch that cube. The book opened in his mind, and he found himself perusing both at the same time. He could combine the two, creating links between otherwise disparate material, comparing and contrasting different opinions, analyzing data in one using the theory in the other. On impulse, he reached a finger out to touch a third book, and that opened as well, adding its contents to the controlled maelstrom of information whirling through his mind. The potential of this method of learning was limitless! Of course, comprehension proceeded at the same pace as it had when he'd been reading only one book at a time, but the ability to arrange the subject matter in any way he wanted made everything so much easier, so much more interesting. Smiling eagerly, he lost himself in his favourite subject.

Thus, he was still perturbed when he realised that after reading and studying for half an hour, a consideration of the problem he'd originally come to the library for revealed that he'd found nothing to help him with it. The calculations still didn't come out, and he couldn't figure out what was wrong. He reviewed the original theory and data, then compared it to that in the three books in his head and... _No. Wait. That._ There was an anomaly... No, it wasn't an anomaly in the subject matter. It was more like something that didn't belong. He could tell, perhaps by the way it felt, which information came from which of the three books, but that bit there didn't belong to any of them. Upon closer inspection, the mote of information expanded in his mind. _A fourth book?_ Opening eyes that he hadn't realised had closed a long time ago, he looked down to verify that his fingers were only touching three cubes. But there was definitely a fourth book open in his mind, and it felt like it might just be too much for his untrained psyche to handle at the moment. _But where is a fourth book coming from?_ Somehow, he knew it wasn't one of the others on the floor in front of him. _Then where?_ He tried to feel for it, and immediately regretted it. Information - garbled streams of words, images, and sounds - flooded his mind, and grabbing his head, he tried to shut it out, to no avail. Blazing golden light burst from his eyes as he grunted at the sudden crushing pain, and he crumpled to the floor.

. _ . _ . _ . _ .

The first thing David was aware of was a dull throbbing in his head. He tried to adjust his position on the pillow but nothing alleviated it and he pulled a hand out from under the thin blanket draped over him to press at his temple. The pressure seemed to ease the pain temporarily, and he opened his eyes to see Jenny standing over him, her wide eyes worried.

"Hi," he croaked.

Without taking her eyes off him, she called, "He's awake, Dad," off to her side, then stroked a tender hand down David's arm. "Are you all right? How are you feeling?"

"My head aches." Pulling out the other hand, he continued to press at his temples, confirming his location as he massaged: the medical bay. "What happened?"

"I was just going to ask you that." The Doctor appeared on the other side of the bed from Jenny, an unknown instrument in his hand and his glasses perched on his nose. Pressing a couple of buttons, he waved the silver implement over David from head to toe.

"I don't know. I don't remember." Things that happened before he woke up here were very fuzzy. "How did I get here?"

"Dad carried you," Jenny replied. "Couldn't just let you lie there on the floor, you know."

David quirked her a smile and caught her hand, squeezing it then holding on lightly. "Thanks. Wow. Everything's just a haze in my head."

"Maybe this will help you remember." The Doctor turned to pick something up from the nearby counter and turned back, holding up David's tablet and book, and six translucent cubes sitting on top.

"Oh! The library!" Appalled at how much he'd forgotten, David dragged a hand down over his mouth.

"We found you on the floor in the crystarium." The Doctor swept the cubes up in one hand and deposited the other objects on the counter. "You'd been reading these, I gather?"

"Right. Three of them. At the same time." Suddenly uncertain, he frowned at the Doctor. "That's okay, isn't it?"

"Perfectly normal. It's what the crystarium is for, efficient processing of information. Perhaps a little ambitious when you're not used to it." The Doctor placed the cubes on the bed next to David. "How did it feel?"

Tossing aside the blanket, David pushed himself up to sit. "Glorious. I never imagined this could be put to such use." He tapped his head.

"Then what happened?"

Scrunching his eyes shut, David pinched the bridge of his nose as he tried to remember. "I was... No... There... there was something wrong. Something didn't fit. It didn't belong there."

"What was it?" Crossing his arms, the Doctor thumbed his chin as he listened.

Bits of memory floated just within David's grasp. "I'm not sure. Something. A thought. No... More like I was reading another book. A fourth book. Yes. That's what it felt like." He stared down at the crystals next to him. "But I was only using three."

"Did that fourth book hurt?"

"No. It was... Oh, it's all hazy. I think... I think I tried to look at it, and then I woke up here." Jenny's hand tightened in his in commiseration.

"Yes, yes," the Doctor murmured as he gazed at David, the lack of focus in his gaze betraying that he was lost in thought.

"Are four books too many?" Jenny asked, eyeing the crystals with a nervous frown.

"Shouldn't be," the Doctor murmured, then jerked himself back to the present. "Neither of you are used to using your abilities, so you might have trouble organising and controlling four books at once, but it shouldn't be harmful."

"Then is something wrong with me?" asked David. "Well, other than everything else that's wrong with me."

"I'm not sure." Lost in thought again, the Doctor rubbed a hand over his jaw, mirroring David's pensive gesture minutes earlier.

That admission shocked David. The Doctor was always quick to reassure those in distress, often concealing information to prevent worry or panic. The statement not only offered no comfort, but revealed that the Doctor both had no concept of what the problem was and felt it was important. Suppressing a shiver, David glanced down at himself. _What could it possibly be this time?_ He cleared his throat. "All right. Tell me what you know."

"That's the problem. I don't know anything." The Doctor spun and pulled the monitor from the wall, extending the bracket so that David could see it clearly. "I did all the scans and tests I could think of, and -"

"And you can't conclude anything because you don't know what I am." David glanced over the monitor to confirm his suspicion, then settled back with his arms crossed, his shoulders curved and petulant.

"Well, yes, if you put it that way." Running a hand through his hair, the Doctor continued to peer at the readout. "It doesn't help that I'm not a doctor. I mean, I can tell that your brain structure is mostly Gallifreyan, but the parts that aren't, I can't tell if they're human or something else or..." He faltered.

"Or something that's not right." David sat as still as a stone, and Jenny hopped up on the bed to throw her arm around his shoulders.

"We'll figure it out, Big Brother." She leaned into him, squeezing affectionately, then ruffled his hair. "We should eliminate the obvious first, don't you think?"

"The books?" David eyed the crystals on the book next to him.

"Yes. See if reading four books causes it again." She glanced up at the Doctor, who nodded his approval of her proposal. Turning, she studied David's face to gauge his apprehension. "If that's okay with you."

"Yeah. I'd like to know..." David didn't think that reading the four books at once, or even all six books, would cause him any discomfort, much less make him pass out, but the thought of trying again made him shiver. If that was the problem, he wouldn't be able to use the crystarium to its potential and the anticipation of that regret clenched his hearts.

"All right." Jenny hopped off the bed and circled around David to look at the six crystals on the bed. As she separated them with her fingers, she gasped. "Oh! That's fascinating!"

"The books in your mind?" David grinned. "Brilliant, isn't it?"

"It is," she breathed. She kept a finger on one of the cubes. "I can see the whole book. Oh, I could learn so much this way." Removing her finger, she stepped back to let her brother work with them. "There."

David placed a finger on the first cube and took a moment to open a chapter. He then began touching fingers to other cubes and inspecting their information before adding more. It wasn't long before he had all six books open in his mind. "There. It's done. I have them all open now."

The Doctor stepped forward to wave his silver instrument over David as he spoke. "And how does it feel? Is it difficult?"

"No." His eyes were unfocused and twitching back and forth as he concentrated on wandering through the books in his mind. "A little disorientating, I think because I don't know what I'm doing yet. But it's not hard and it doesn't hurt."

"Do you sense another book like you did before?"

"No, not at all. All of the information I'm looking at is from one of these books here. I can tell. And I'm running out of fingers." Sighing, he pulled his hands from the crystals.

The Doctor was peering at his instrument. "Nothing here, either. So that wasn't it." He tapped the tool against his lips as he thought. "What else could it be?"

"We could go back to the crystarium and try whatever it was that David did again," suggested Jenny.

"No. Only as a last resort." The Doctor eyed David up and down. "Whatever it was caused him to pass out, and that isn't healthy for anyone, human or Time Lord. I'd rather we not put him through that again if we don't have to."

David threw up his hands in helpless frustration. "Then how do we figure out what happened? It's all conjecture at this point."

"No, there's another way. Though…" and he ran his tongue across the edge of upper teeth, "I'm not sure you'll allow this. I could look into your memories and see what happened. I might see more than you can consciously remember, and I might be able to interpret it better. But, well, you'd have to let me, and I'm sure..." The Doctor's words faltered.

Looking up, David's eyes met the Doctor's. Though at this point he'd gotten used to having a twin, seeing his own face feature-for-feature on another man, there were still moments when he had the uncanny feeling that he stood in both places, both of him staring at each other. It never failed to unnerve him, but this time, he also felt that other self drawing back, as if the Doctor was shying away from the psychic touch they always shared. His hearts fell; the Doctor truly didn't care at all about him. _All I am is a puzzle to him, at best an interesting question. Well_ , he sighed inwardly, _at least I'm that much._

Trying to hide his disappointment behind a nonchalant facade, David nodded. "Sure. You can do that. There's not much in here that you don't already know." He breathed deep to bury his bitterness, then slid off the bed and straightened to his full height in front of the Doctor.

"I'll be careful. I'm only looking a couple of hours back, at most." The Doctor seemed to hesitate before raising his hands around David's head.

"Yeah."

Placing his fingers on David's temples, the Doctor closed his eyes and concentrated. David closed his own eyes and, opening his mind, tried not to flinch as the other man's consciousness touched his, then pushed in, exploring. True to his word, the Doctor was working backwards through his memories, very pointedly bypassing everything else in David's conscious and subconscious mind. As he waited, David observed his methods, and he noticed what Reinette had discovered, that it would be easy to follow the Doctor's thought back into his mind. But unlike Reinette, David didn't presume to do such a thing, and he certainly didn't need to invade the Doctor's privacy and provide more fuel for his dislike.

"Yes!" The Doctor's sudden exclamation made both David and Jenny jump, and David's eyes popped open.

"What is it, Dad?" Jenny's eager voice broadcasted her anxiety for her brother.

"What happened, it's right there, plain as day! But why?" The Doctor frowned as he continued to explore. "Hold on. Hold on a tick. Maybe… No. That's not it. How about…?" Breaking off the contact, the Doctor grabbed a tool from the counter behind him and, adjusting it, spun back and thrust it in David's face. As his target sneered and swatted at his hand, he peered at the readings, then pounded the tool against the heel of his hand and read it again. "No! I just don't get it!"

"What did you see?" asked Jenny, trying to goad her father into sharing.

"It was completely obvious!" he exclaimed. He jabbed a finger at David. "You saw that bit that you didn't recognise and you tried to trace it, right? That's the thing! Your mind was flooded with information! Just flooded!" He swung his hands around like he was swamping David with a wave of water. "Gigabytes, terabytes, maybe more, all at once, bam!" He punched the air, just missing David, who started back in surprise. "You couldn't handle it - no one could handle that - so your mind just shut down. Fweeoomp, and you were out!" With another swing of his arm, he spun all the way around, ending with a triumphant grin. "It didn't even last long enough for you to remember it. There's just the barest ghost of it left in your mind."

Ignoring the Doctor's jubilation, David bit his lip. "I don't remember that at all."

"You won't. What little memory that's left is just a whisper." Still beaming, the Doctor tapped the tool to his lips. "But why'd it happen? Where'd it all come from? I mean, it's not from these books. What's here is barely a thousandth of what I saw swamp your brain, and not a trace of it is left, though you still remember what you read from these, don't you?"

David thought for a moment. "Yes, I remember what's in those books. I can't recite it, but I can tell you some of the things I remember reading."

"Right. So we've no idea where that information came from, or why it appeared like that."

David shrugged. "It sounds to me like something's wrong with my brain."

Jenny gaped at him, appalled. "Why would you think that?"

"Because there's always something wrong with me!" Finally giving in to his frustration, David stalked off and paced back and forth, his eyes shimmering gold. "This or that is always broken. My regeneration. These voices in my head, which I might note are bloody silent when I need them right now. I'm sure that this is something like my brain not being able to grasp these concepts and sicking them up in a garbled mess."

Cocking her fists on her hips, Jenny adopted a firm stance to try to dispel his resentment. "David, we don't have any evidence that your brain is not working correctly."

Scowling, he shot back, "You also have no evidence that it _is_ working correctly."

"Well," the Doctor drawled, "that we can -" He broke off and coughed. "Er, well, I suppose we can run more tests." As David whirled back, the Doctor spun away to the monitor, ducking his head in an obvious attempt to conceal what he was about to say.

"What was that? What were you going to say?"

"Nothing important. Here. A neurochronoterical map could tell us just how -"

"Doctor!" David glowered at him, cutting him off. "You were going to suggest something. I know all of your tells, better than you do."

The Doctor's shoulders slumped. "It's nothing, David. It's nothing you want to do."

"I'll be the judge of that. Tell me what you were going to say."

The Doctor turned back, tugging on an ear. "Well," he drawled, "I can't really gauge the health of your brain with any of these instruments, since you're something new, but I can gauge the health of your mind. I can use this." He tapped his own temple. "But, to do that, I'd have to go very deep." He gestured, painting the diagram of the layers of the mind in front of him. "Down into the fourth layer. All the way in."

"Oh." David didn't like the sound of this.

"And you'd have to let me, willingly. It'd be like baring your soul to me. And that deep in, well, I'd be bare to you, too, if you'd look. I'm honestly not that comfortable doing this." He swallowed, his Adam's apple bobbing visibly. "This is more like something a bonded pair would do, which, well, you understand..."

"No. No way." David stepped back with his hands waving his refusal. He wasn't completely clear on what the Doctor was saying, but he understood enough to know that neither of them would want this. This was some kind of deep probe that sounded like the two of them would almost merge, and that was out of the question. He paced off away from Jenny. "There's got to be some other way."

"Well, we certainly can look for other options. But honestly, David," the Doctor shrugged, "it isn't very different from what we've already done. It's a level deeper, a connection that we couldn't have -"

"Wait." David had spun back and was staring suspiciously at the Doctor. "What are you talking about? What have we already done?"

"When we..." The Doctor faltered, then his jaw dropped in horrified realisation. "You don't remember!" Spinning in place, he smacked his forehead with the palm of his hand. "Of course you don't remember! You had to forget and we never fixed that!" Jenny and David stared at him.

"Doctor..." began David.

"This!" Before David could react, the Doctor bounded over to him and cupped his twin's cheek in his palm. He stared into his eyes for a moment, then David jerked, stumbling backwards as a deluge of memories swamped his mind.

As he clamped his hands to his head, David's unfocused eyes, glowing pale gold, twitched back and forth, as if he were watching a film on fast-forward. His jaw dropped in disbelief as the images flashed in his mind, of the Doctor appearing to him in the cloister room to console him, to forgive him for what he'd done, and, amazingly, to approve of him. And then... "We... we touched..." David breathed.

"Yes." Suddenly subdued, the Doctor whispered the word. "You wanted to know me. We joined our minds and we saw each other from the inside."

David nodded. "But we couldn't connect completely because I was human. Without the expanded consciousness and the psychic ability, I couldn't meet with you as an equal." Somehow, he understood the difference. This knowledge was instinctual.

"More than that. Both individuals must be Gallifreyan. This kind of connection doesn't work between species."

Shaking his head slowly, David continued to mull over his newly-awakened memories. "We touched. I saw you. I _was_ you. It was gl -" Catching himself, he schooled his expression to neutral, resolving to not display any sign that he had appreciated the brief but intimate connection with the Doctor, who was wringing his hands with nervous energy. His eyes darkened. "What you're proposing is similar, but deeper, and has far-reaching ramifications."

"Right!" The Doctor clapped his hands and began busying himself gathering his scattered tools and putting them away in the cabinets. "We'll figure this out. There must be something we can do to find the cause of the problem."

David knew exactly what that meant - could read the Doctor's regret at that encounter in every movement - and he completely agreed. Whatever kinship he might have felt with the Doctor back then had long since dissolved, and doing something like that mental touch again would just make everything worse. He adopted an eager but professional attitude. "We can experiment in the crystarium as Jenny suggested. I'm not afraid and I'd like to know what happened."

"Yes," the Doctor agreed, "and this time, I'll be watching and scanning you. We should be able to observe whatever it is as it's happening. Maybe even stop it in time."

"Well, you wouldn't want to cut short the experiment just to save me one blackout. That's hardly conducive to gathering valid -"

"Wait." Jenny cut across their ramblings. "You're not going to search his mind?" She was plainly confused and surprised, her eyes flicking back and forth between the two, trying to figure out what they were doing.

"No. It's not really a good idea, Jenny," the Doctor replied with the tone of voice of a parent trying to sugar-coat reality for his child.

"Why not?" She shrugged her question. "You're already the same person anyway. It's not like it'll be much more than you already are."

Their jaws dropping open, the Doctor and David sputtered at Jenny identically. "Wh- what?" David finally coughed. "We are in no way the same person."

The Doctor managed to compose himself far better than his twin did. With a condescending smile, he admonished his daughter gently. "You know very well that we're not the same person, even though we look identical." His eyes flicked with irritation at David. "Except for the hair."

Rolling her eyes, Jenny shifted with the exasperation of a teenager who knows that the adults think she's ignorant. "Oh, come on! I know you both try to hide it so that I don't feel uncomfortable with you, but I can always feel it, in here." She tapped her temple with a finger. "Your minds are entwined. Sometimes I almost can't tell you apart." She pointed at each of them in turn. "You're Dad, and you're Big Brother, but together, you're so much more. And you need each other."

The Doctor and David stared at each other, identical eyebrows cocked high. Then, as one, they turned to Jenny and snorted out an incredulous negation. "Nahhh! He doesn't like me one jot!" "No! He doesn't even want me here!" Spinning back to each other, they exclaimed in an eerie stereo broken only by a difference in accents, "What? Why would you think that?"

Thrusting his hands in his pockets, the Doctor stared at David. "Of course I know you've always resented me! It's not like you've kept that hidden at all. I know you blame me for dooming you to this life, and you certainly didn't want to come with me when I offered."

"That's rubbish!" David exclaimed. "I wouldn't exist if it wasn't for you, and you've been my hero since I was three! Why would I hate you? Why wouldn't I want to be here with you, travelling the universe?" He thrust an accusatory finger at his twin. " _You're_ the one who doesn't want _me_."

"How did you get _that_ idea?"

David rolled his eyes, shaking his head. He'd long reconciled himself to his place in the TARDIS and was far more upset that the Doctor thought he needed to pretend to want him. "I've always known that I remind you of all the things you don't want to remember. I can see it in your eyes every time you look at me. And I know that you just feel obligated to take care of me until I can survive on my own. That's been obvious from the start. Did you really think I wouldn't notice you and Bowtie juggling me around? He never wanted me in the first place, tried to foist me off on Amy's aunt the moment I arrived in the TARDIS. You just took me so that he could get on with his life."

"What? No no no!" The Doctor tore at his hair in astonished frustration. "We weren't playing hot potato with you. We both wanted you with us. If anything, we were fighting over you."

Incredulous, David snorted and turned away. "You were not."

"Yes, we were." The Doctor strode over to David, ducking around him so that he was forced to look at and listen to him. "How can you even think that I don't want you here? You're a Time Lord! Even just for that, I'd want you here. But more than that, you're you! Brilliant old you! The one that..." He faltered, his eyes unfocusing and darting back and forth. "Oh. That's what it was. You've been holding back," he murmured, suddenly subdued. He stepped back, his tongue flicking over his lips. "I felt it. You weren't fully engaged in our link, because you thought I wanted you gone and you were afraid I'd just abandon you." Appalled, he scrubbed his hand down over his mouth. "And me, stupid, _stupid_ Doctor, I should have known! I held back because I thought it meant you hated me and I didn't want to scare you away. Oh!" Smacking himself in the forehead with both palms, he spun away and paced across the room. "I should have seen that! I should have known!"

Biting his lip, David peered up at the Doctor from under a bowed head. "You really don't mind having me here, teaching me, training me?"

The Doctor spun back to face him. "Mind? I _want_ you here, David. Why can't you believe that?"

David shook his head. "I just can't."

"Yes, you can. Think back to the cloister room. We touched then, and it may not have been a full connection, but I would never have agreed if I didn't want to do it."

David closed his eyes, reliving the memory of merging with the Doctor, the imperfect juxtaposition of two minds, so alien to each other. With the benefit of hindsight and a Time Lord consciousness, he could better interpret what he had sensed in the Doctor, and his eyes popped open in surprise and disbelief. "You really do approve of me," he murmured.

"Much more than that, David. 'Approve' is such a sterile word. I didn't lie when I said that I'd hoped we could be friends and brothers." Suddenly uncertain, the Doctor looked away. "If you want."

Stunned, David dragged a hand down over his mouth, then straightened and stepped directly in front of the Doctor. "Search my mind, Doctor. Find out what's wrong with me."

The Doctor glanced up at David, and his dark, shadowed eyes cleared, sparkling as they met with his twin's. He placed his fingertips on David's temples and closed his eyes.

The first time David and the Doctor had touched, back in the cloister room, David's human mind had jerked uncomfortably and exploded into Time Lord awareness, and there had been limits to how much of what he saw that he could comprehend. The second time, only a number of hours ago, when David tried to break through the Doctor's mental defenses, they'd been opposed and the sensation had been disturbing as their minds slid against each other with high friction. This time, as they willingly met each other, they blended seamlessly, establishing a continuum that flowed from the core of one man to that of the other. The sensation was achingly familiar, and David realised why: he and the Doctor had once been one person. Somehow, he felt like he had come home again, and now he understood what Jenny had meant when she said they were so entwined that she couldn't tell them apart.

He knew the Doctor was searching his mind, evaluating its health, and as he waited, he soaked in the Doctor's consciousness, not seeking or exploring but instead simply letting it flow through him, his forty-year-old mind marvelling at the wonders he saw in this nine-hundred-year-old memory - _far more than that, if the Doctor wasn't such a liar_ , he laughed to himself. Time seemed to come to standstill as he let himself absorb all that he could, and his hearts clenched knowing that this must end soon.

"There," the Doctor murmured. "There. I see it." After another moment, he breathed, "Ohhh..."

David's eyes popped open to see an incredulous smile on the Doctor's face. "What?"

Jenny bounced next to them, her fingers twitching, obviously afraid to touch either of them in this delicate state. "Is David okay?"

The Doctor withdrew his hands from his twin's face, breaking the connection between them. Rubbing at his eyes, David shuddered at the sudden, cold silence in his head whilst the Doctor replied to Jenny. "Yes, he's fine." He flashed a smile at his daughter, then threw his head back to stare at the ceiling. "It's so simple. It was staring us right in the face."

"What was?" David demanded, anxious for the diagnosis.

Pressing the tip of his tongue to the roof of his mouth, the Doctor regarded David with a thoughtful gaze for a moment before responding. "You thought there was a fourth book. Of course there was a fourth book! And a fifth. And a sixth. And a six hundredth and a six thousandth! You were in the crystarium!" He spun with his arms wide as if that explained everything.

"I know that!" David growled. "And?" His impatience shook him, and he clenched his fists. Sometimes the Doctor's circumlocutions were infuriating.

"And... you're not a touch telepath."

David frowned. "What? Of course I am. We proved that earlier today."

"No, you're not." Jamming his hands in his pockets, the Doctor leaned forward, his jaw jutting forward in playful mockery of his twin. "Your telepathy doesn't require physical contact."

David simply gaped at him.

"That's just it! You've never tried before. Using your abilities, I mean, and, in fact, you've been holding them back, to stay away from me." Embarrassment and regret for that whole situation flitted across the Doctor's face. Then, holding his arms out, he stepped back, away from David. "Tell me what I'm thinking."

Frowning, David concentrated for a moment. "A can of purple paint," he gasped. He goggled at the Doctor's nod and proud smile, then stared at his own hands like they had suddenly withered to bone. "I'm not touching you!"

"No, you're not. And that's what happened in the crystarium." He picked up a crystal book and held it in front of David's face. "You connected with a book you weren't touching, and when you tried to figure out what it was by looking around, you accidentally opened yourself up to all seven thousand, three hundred, and fifty-one books in the room, which snuffed you like a waterfall on a candle." He flicked the cube onto the counter.

Shaking his head, David couldn't accept the explanation. It didn't make sense that a hybrid of Time Lord with a lesser species could have an improved version of a Time Lord ability. "But how is this possible?"

The Doctor shrugged. "Could be just the way you're made up. Touchless telepathy isn't unheard of in Time Lords. More likely, it's because you're part human."

"But you said humans aren't telepathic," Jenny protested.

"No, I said the ability is rare in humans. They all have latent psychic ability, but in a rare few, it's active." He wagged a finger at David. "Remember Tim Latimer. When a talent like that manifests in humans, it never requires touch. You've the methods of a human with the power of a Time Lord."

David blinked at the Doctor as he considered the implications. He knew there had to be something useful he could do with it, but all he could picture was the Polthite, Ana, drilling a hole into his mind and scraping out his thoughts. He could now do the same thing to someone, but from across the room. "But that's… that's… that's dangerous."

"Nah!" The Doctor stared at David in surprise, his left eyebrow twitching. "Why would you think that? You don't even know what you can do from a distance. Even what we did just now, that deep connection, I expect you can't do that without a touch, because it takes so much more power and skill. Well," he drawled, "maybe after a lot of training and practice." His words didn't seem to reassure David at all, so he stepped forward and grasped his shoulder. "Honestly, it depends on what _you_ choose to do with it. And, knowing you, I have no worries on that front."

David stared at him, unable to decide if he'd said what he did simply to put Jenny more at ease, rather than himself. Both he and the Doctor knew it wasn't as simple as that, that even with the best of intentions, it was too easy to abuse any power they wielded; after all, David himself was a direct consequence of such a failure. The Doctor seemed to be ignoring that event, regarding David with a slight smile that communicated his confidence in his twin's strength and morality, and David couldn't take it anymore. Jerking his shoulder out of the Doctor's grasp, he spun away, wringing his hands.

Jenny came up next to him and laid a hand on his arm. "Come on, Big Brother. It's just another skill, another thing to learn to do. Think about the crystarium and how much you can learn from it with this ability. That is, if you can filter what you hear from it."

She was certainly right, that there were amazing things he could do with his telepathy, but... There were so many ways things could get away from him, spiral out of control. So many stories hinged on the best of intentions gone sour, on people believing to the end that the evil they were perpetrating was right thing to do. "No," he murmured. "I don't want this."

With a worried frown, Jenny opened her mouth to comfort her brother, but the Doctor's hand on her shoulder stopped her. "David," he intoned gently, the undercurrent of concern in his voice compelling David to look up at him, "you don't have a choice. Or rather, you do, but it's not a choice of being telepathic or not. Your choice is how you use it, whether you will use it for the right reasons or not, or maybe not use it at all. Thing is, you have to make that choice with everything you do, big or small. This is no more inherently good or evil, or dangerous or safe, than anything else."

Daivd rubbed a hand over his mouth and pinched the bridge of his nose. "It just feels so wrong."

Nodding, the Doctor stepped back. "I understand. If you don't mind, I think this is all too new to you. It feels alien, doesn't it?" David nodded in response. "Give yourself some time. You might find in a few days that the alienness fades, and when it does, your fears may dissolve."

David stared back the Doctor, the muscles in his jaw twitching as he considered how to respond. "Do you really think my worries are so easily dismissed?"

"No. Not at all. But I think you'll approach things with a bit more objectivity after you've had a chance to see what it all really means to you."

Curling an arm across his chest, David tugged at his ear as he gazed at the Doctor, trying to glean any shred of wisdom from the older Time Lord's expression. Failing that, he sighed and nodded. "It all comes back to time, doesn't it? Give myself more time. I can't expect my answers to come quickly and easily, can I?"

"No, they never do. That's something that's taken me centuries to learn, and I still forget. Oh!" the Doctor exclaimed, his countenance lighting up. "I was wondering, what were you doing in the crystarium anyway? I thought the main library would satisfy your thirst for knowledge for at least another couple of months."

David shook his head, snorting with frustration and disgust. "Torturing myself with temporal mechanics, mostly."

"Torture?" Jamming his hands in his pockets, the Doctor peered at David. "It isn't the easiest discipline, but I thought you were enjoying it."

"I was!" Those two words dripped with frustration and disappointment. "It's a fascinating subject. Grades 1 and 2 were riveting! Then I got into grade 3 and the last few chapters just stopped making sense." Turning to stride across the room, he tore at his hair. "Now I'm stuck in chapter five and getting nowhere, and nothing I've found in the library sheds any light on it."

"Is that the calculation of spatio-temporal variances in higher-order dimensions?"

"That's the one. And more, but that's where I'm stuck." David spun to frown at the Doctor, surprised that he remembered the chapter so well, as his own education had been centuries in the past.

Pulling off his glasses and dropping them in his pocket, the Doctor shrugged as he spun to turn off the lamps along the medbay workbench. "Oh, that one's all wrong."

David nearly choked upon hearing that. "What?" he blurted.

The Doctor continued to explain as he shut down the facility. "Sevratimonlan's work is rubbish after grade two. He teaches the basics like no one else, but he's got no grasp on even the intermediate concepts. You'll want to pick up Omitendram's papers on the subject instead."

David ran his hand through the mess of his hair. "I've been through all of that and more, but none of it fits! And you said we need to know the texts up through grade five!"

"I did. It's a great lesson in not trusting everything you read." He shot David a mischievous grin as he moved to the next bench. "When I took the class, we spent the entire term on it, and after the final exam, the professor told us how much of it was wrong, how much we'd have to unlearn." Spinning back to face them, the Doctor grinned widely. "Oh, you should have seen Ushas - the Rani! Hopping mad, she was. Stormed out of the room. She didn't catch all the errors, and she should have."

Still clutching at his hair with one hand, David stared at the Doctor, his mouth hanging open. "So you knew it was all a waste of time?"

"Oh no," the Doctor breathed, rolling his eyes in self-mockery. "Barely understood a word of it. How could I tell it was wrong? None of us knew. We found out later that it was a standard test of understanding. Only the most brilliant temporal theoreticians could tell that something was wrong with Sevratimonlan's framework and would not be able to produce the results he did." The Doctor winked at David as his implication sunk in.

"What, me?" One eyebrow shot up in incredulity.

The Doctor wagged a finger at David as he spun around the room, picking up instruments and stowing them away in cabinets. "I've told you before. Your grasp of temporal mechanics is stellar. You could probably resurrect much of Time Lord temporal science yourself, if you wanted to devote your time to it."

David laughed and shook his head. "I don't believe you. Me, a temporal engineer? That's beyond insane."

Jamming his hands in his pockets, the Doctor turned back to him and rocked on his toes as he spoke. "No, the person you don't believe in is yourself. How many times did you try to work through the problem? I'm guessing that your first instinct when you couldn't solve it was to question yourself and not the proposed solution in the book, despite your reservations about the validity of its theories." When David bit his lip, the Doctor gave a sly grin. "I'm right, aren't I? You've got to assess your own strengths objectively and believe in yourself."

David shook his head. "That's unbelievable. I've never excelled at science. It's just like this telepathy thing, isn't it? Something like my human side contributing something special."

"Whatever caused it is irrelevant. It's you who's brilliant." The Doctor's faith in David shone in his proud grin. "See? Becoming who you are brings good things as well as bad."

Considering carefully, David nodded. "I suppose I just see the bad things. There is a lot of good," he admitted. "Like both of you." He quirked a tiny smile as he glanced at the Doctor and Jenny in turn, then shrugged. "I don't know. I just… I just need to figure this all out."

Closing the last cabinet, the Doctor turned and nodded. "I understand. Take all the time you need."

"We'll be here if you need anything. Someone to talk to." Jenny hopped over and briefly hugged her brother's arm.

"Thanks. Yeah, thanks." David thumbed over his shoulder. "I'm going to go pull Omitendram's papers again. I'll be up in the library." Spinning on his heel, he pulled the door open and disappeared into the corridor.

. _ . _ . _ . _ .

Several hours later, David leaned back in his chair and puffed out a breath as he surveyed the large sheet of paper in front of him. Completely covered with tiny interlocking circles and lines in his own handwriting, it, along with the three other similarly-sized papers beneath it, boasted his calculations of the spatio-temporal variances in the Sapari Cluster, derived from first principles and accounting for gravitic bodies and extradimensional warping. Pushing his glasses up on his nose, he hopped up and reached all the way across the table to pick up the book he'd kept out of arm's reach so he couldn't be tempted to peek at it for hints. He plopped back in his seat and paused a moment to glance at the tome's title, Omitendram's _Discussions on the Effects of Dimension and Mass on Temporal Fluidity,_ then flipped it open to the appendix. Paging to the experimental results from the mapping of the cluster, he set the book down next to his calculations and compared each number, circle by circle. A tentative smile slowly spread across his face as he verified that each calculated figure matched its experimental counterpart well within tolerance. _It works. The theory is sound, it predicts the experimental results, and I understand!_ Out of respect to the TARDIS' library, he refrained from jumping out of his chair and dancing around whooping, but he did allow himself to pump a victorious fist.

Finally giving himself a moment to relax, he dropped his glasses on the papers in front of him, then propped his elbow on the table to rest his chin in his hand. It had been a long, exhausting day, full of surprises, most of which, he had to admit, were good. He still didn't know what to think about his telepathy and he was nervous about exploring that ability. In addition to harboring a moral objection to its methods and effects, he had to admit that he was upset that this was just another way in which he was different, neither a Time Lord nor a human. He didn't know why it bothered him so much that he couldn't put a firm label on himself, but it did.

Whatever he was, at least the Doctor and Jenny accepted him. Even after all that had been said and done today, he still hesitated to claim that he was part of their family, but his apprehensions about the Doctor's attitude toward him had vanished. Closing his eyes to better sense the others, as he had done many times since leaving the medbay, he could feel the Doctor as clearly as he could feel Jenny, with no hesitation, suspicion, or reluctance on either of their parts, and the TARDIS now felt like home to him, the first and only home he'd ever had in this universe.

But there was one more thing. When the Doctor had withdrawn from his mind, leaving what felt like a yawning silence after that glorious psychic communion, David had noticed a quiet presence, a snatch of melody floating behind his thoughts, its presence warm and comforting. If he closed his eyes and let it wander through his mind on its own, he could identify it: a shadowy impression of the consciousness of the Doctor, a remnant of their brief but intimate connection. This was the result of the deep bonding, what couldn't have happened when they'd touched when David was human, and as he savoured it, a tender contentment shone in his eyes: it meant that he would never be truly alone again, and that though this Doctor was fated to die and change soon, he would live on in one small way, in him.

Abruptly jumping up from his seat, David gathered his papers and books and strolled out of the library. It was time he joined the others, truly became a part of this tiny microcosm floating in the time vortex, before he plunged himself back into his studies. Besides, he was gasping for a cup of tea and Jenny hadn't pinned him to the mat quite as many times as she liked to yet today. It never did to disappoint his little sister, and he mentally prepared himself for another long bout of body- and ego-bruising as he headed for the kitchen.


End file.
